Teletypewriter system



July 16, 1940. w. B. MARTIN 2,208,192

' TELETYPEWRITER SYSTEM Filed June 17, 1958 SUBSCRIBER B CENTRAL OFF/CE POLAR/ZED SUBSCRIBER A 'INI/ENTOR W8. MA 7'//V A 7' TOR/VE V Patented July 16, 1940 UNITED STATES TELETYPEWRITER SYSTEM Wade B. Martin, Westwood, N. J., assignor to American Telephone and Telegraph Company, a corporation of New York 1 Application June 17, 1938, Serial No. 214,298

1 Claim.

This invention relates to improvements in teletypewriter systems and, more particularly, to means for conditioning a subscribers station set for improved remote control of its teletypewriter motor.

For the purpose of illustration, the invention is described with reference to printing telegraph machines of the type shown in Patent 1,904,164 granted April 18, 1933 to S. Morton et al. and to a teletypewriter system having a teletypewriter central oflice and subscribers teletypewriter station set of the type described in Patent 1,965,383 granted July 3, 1934 to C. C. Lane in which the motor of the teletypewriter at the subscribers station is adapted to be started by remote control by reversing the polarity of the current normally flowing over the line, and is designed to be stopped by remote control in the manner described in the aforementioned Morton et al. Patent 1,904,164 and also in Patent 1,931,672 issued October 24, 1933 to S. Morton et al. by transmitting two successive preassigned permutation code signals over the line as will be discussed in more detail hereinafter. The dis 25 closure of these two. Morton et al. patents and the disclosure of the Lane patent are each incorporated herein by reference as a part of this specification. It is to be understood that the invention is not limited to use with teletypeo writers of the type disclosed in Morton et a1. Patent 1,904,164 and is also not limited tothe type of subscribers station and central ofiice shown in the Lane patent nor to the remote control means of the type mentioned above, but that 35 the inventionis described with reference to the apparatus disclosed in the above-mentioned patents purely for illustrative purposes and that the invention is capable of application to other forms of apparatus and to other systems of re- 40 mote control. v

As is described in Morton et al. Patent 1,904,164, this type of printingtelegraph machine is provided with apparatus which is designed to shortcircuit the sending contacts in the teletypewriter 45 when the teletypewriter is in its receiving condition. However, this shunt path is not always completed and, even when it is completed, it does not short circuit the subscribers break contacts and for these reasons a certain amount of trouble 50 has been experienced from three sources.

One class of trouble has been caused by an operator improperly transmitting a series of successive remote stop signals in spite of instructions to the contrary. Reception of such a succession of stop signals sometimes results in the remote.

subscribers teletypewriter stopping with one of its sending cams in an open position thereby leaving the line open which is undesirable as it prevents a disconnect signal from being efiected, prevents the subscriber from beinghcalled and also prevents the subscribers motor from" being started by remote control.

A second source of trouble is caused by im-, proper adjustment of the contacts in thesubscribers break mechanism which is of the type 03 described in Patent 1,980,284 issuedNovember, 13, 1934 to S. Morton et al. The disclosure of this Morton et al. patent is incorporated herein, by reference as a part of-this specification al. though it is to be understood that the invention is not limited to this type of break mechanism. The break contacts require delicate adjustment and occasionally a maintenance man does. not properly adjust them. This improper adjustment sometimes results in unintentional opera- 20 tion of the so-called transmitting break contact (contact 46 in Morton et al. Patent 1,980,284) when only the so-called receiving or positive break contact (contact 48 in Morton et al.,Patent. 1,980,284) is intended to be operated. This unintentional operation will momentarily open the so-called transmitting break contact and, if the subscribers motor should stop at thistime, it cannot be started by remote control until the subscriber restores the apparatus to its normal.

condition. 9

The third type of trouble results from improper, or unauthorized operation of the breakkey when the teletypewriter is idle. This sometimes happens when some person, such as an office boy, passes through the subscribers office and sees an idle unattended teletypewriter; Upon looking at the teletypewriter and noticing the break key; he becomes motivated by curiosity and presses this key thereby operating the break mechanism which then cannot be restored by remote control until the subscribersmotor has been started by the local operator. Ordinarily, the operator at the remote control station or central oifice does not realize the cause of the trouble and generally attributes it to something being out of order in the subscriber's machine. This sometimes results in a maintenance man being sent to the subscribers station which is, of course, a needless expense. s

Accordingly, it is an object of this invention to reduce the above'types of trouble in teletypewriter operation, caused by weaknesses in the human element which is necessarily present, by conditioning a subscribe-rs station set for im-,'55

proved remote control of its teletypewriter motor.

It is also an object of this invention to close a short circuit path around the line relay, sending contacts, and break contacts in the subscribers set whenever the subscribers local source of power supply is disconnected from his set by either local or remote control.

These objects are attained by modifying the subscribers station circuit, shown in Fig. l of the abovementioned' Lane patent, to include a shunt path across the subscribers sending contacts, break mechanism, and line relay. Since: the subscribers power relay, or motor control relay, is not included in this shunt path and since the shunt path closes the line circuit through the power relay toground, then, even if the sending contacts are open or the break mechanism has its contacts open, there is still. a path closed from the line through the power relay to ground so that a remotely located operator may send control signals over this path. to operate the subscribers power relay which, in turn, closes the subscribers power supply circuit and starts his teletypewriter motor.

These and'other features of the invention will be more fully describedin connection with the detailed description of the drawing which shows a subscribers teletypewriter station set connected througha teletypewriter central ofii'ce to another teletypewriter subscribers station.

The drawing shows two subscribers teletypewriter stations A and B connected together through a teletypewriter central ofiice C by communication channels L1 and- L2. Station A is shown to be a 'subscribers teletypewriter station of the type described in the above-mentioned Lane patent. The '-station apparatus and circuits at the subscribers station B have not been shown in their entirety as it is to be understood that they are similar to those at station The equipment at central ofiice C has not been shown asthis equipment is the same as that illustrated in Figs. 2 and 3 of the aforementioned Lane patent.

Station A is shown to include a printing telegraph sending and receiving unit i having a printer magnet 2, sending contacts 3, break contacts 4, a local source of power supply 5, a motor 6, and remote control contacts I Although the break apparatus is represented simply by contacts 4 for the sake of simplicity, it isto be understood that it actually comprises the break mechanism shown in Figs. 6 and '7 of the Morton et al. Patent 1,980,284 mentioned above. Likewise, the control contacts '7, which are provided for enabling an operator at a remote station, such as station B or central oi'fice C, to stop motor 6,

actually comprise the control contacts 86 and B ll and their subsidiary apparatus shown and described in the above-mentioned Morton et al. Patent 1,931,672.

In addition to the printing telegraph sending and receiving unit I, station A is provided with subsidiary station apparatus comprising start key 8 for enabling'a local operator to start motor 6, stop key 9 for enabling a local operator to stop motor. 5, start relay ill for completing the energizing circuit for motor 5', polarized remote control or power relay H for enabling an operator at a remote station to start motor 6, polarized line relay |2',.control relay l3, ringer 14, local test key l5, and recall key IS. The opera tion and functions of both the printing telegraph sending and receiving unit I and the subsidiary station. apparatus are fully described in the aforementioned Lane patent and need not be repeated here.

In the drawing, the circuit is shown in its idle condition with the subscribers motor 6 not running and a shunt path closed from the winding of relay ll over the bottom armature of control relay 13, which is normally not energized, and over the local test key IE to ground ll. Due to this short-circuit being closed, the subscribers sending contacts 3, break contacts 4, and line relay. l2. are normally shunted out of the line circuit.

The subscriber at station A can start his motor 6 by momentarily operating his start key 8 which closes a path for energizing the start relay Ill. Accordingly, relay I0 operates its armatures and locks-up through a .path over its bottom armature and through the stop key 9. The operation of the top armature of relay l0 starts motor 6 by closing. a path leading from the local source of power supply 5 to motor 6. At the same time.

the operation of the top armature of relay I0 closes an energizing path from the power supply 5 to the control relay [3 which operates its armatures, the top armature switching the line circuit from ground I! over the recall key I6 to the line L1 and the bottom armature opening 0 the short-circuit across the sending contacts 3, break contacts 4, and line relay l2. The circuit is now in condition for transmission and reception of messages.

When the circuit is in its normal idle condition shown in Fig. 1, an. operator at central oflice C can start motor 6 by remote control in the following manner. One side of line L1 is normally closed through the winding of the polarized remote control or power" relay H and over the shunt path to ground H. To start the motor 6 at the subscribers station A, the operator at central office C reverses the polarity of the line current in the manner described in the Lane patent mentioned above thereby operating the polarized relay H at station A. The operation of relay H has the same effect as the operation of the local start key 8 in that it closes a path for enabling power supply to energize the start relay 'III which starts motor 5 and energizes relay l3 in the manner described above to place the subscribers station circuit in condition for tranrmission and reception of messages.

The subscribers station circuit can be restored to its normal idle condition by either local control exercised by the subscriber at station A or by remote control from'an operator at central office C or another connected subscriber as, for example, the subscriber at station B. All that the subscriber at station A need do is simply open his stop key 9 momentarily thereby opening the locking-up circuit of relay l0 and causing it to release its armatures". The release of the top armature of relay l0 opens the energizing paths for motor 6 and relay l3. As a result, motor 6 will stop running and relay l3 will release its armatures, the top armature switching the line circuit to ground I! and. the bottom armature closing the short-circuit across the subscriber's line relay 12, break contacts 4, and sending contacts 3. The switching of line L1 to ground I! insures that the operation of stop key 9 will give a disconnect signal to the operator at the central office C in the manner described in the above-mentioned Lane patent.

To place the subscribers station circuit in its idle condition by remote control, either the operator at central office C or another connected subscriber. as, for example, the subscriber at station B, transmits a preassigned motor stop combination of permutation code signals which are received by the receiving relay E2 to control the printer magnet 2 which actuates other apparatus (not shown in the drawing) to eiTect the opening of the remote control contacts I in the manner described in the Morton et al. patents mentioned above. The opening of contacts I has the same efiect as the opening of the local stop key 9. Consequently, motor 8 will stop and relay l3 will release its armatures to switch the line circuit to ground I7 and to close the short- 'circuit around the subscribers sending contacts 3, break contacts 4, and line relay l2.

Thus, whether the local source of power supply is disconnected from a subscribers set by either local or remote control, a short-circuit will be closed in either case around the sending contacts 3, break contacts 4, and line relay 12 of the subscribers set so that any false operation in the subscriber's printing telegraph sending and receiving unit I will not affect the condition of the line circuit. It insures that, during idle periods, the line circuit will have a closed path through the remote control relay H to ground l1 and that the station set will consequently be in a receptive condition for motor start signals transmitted over line L1 by an operator at central ofiice C or by another connected subscriber, such as thesubscriber at station B.

What is claimed is:

In a printing telegraph system, a printing contacts and also having a motor for operating the printing telegraph set, a local source of power supply for energizing the motor but normally disconnected therefrom, starting means for connecting the motor to the power supply, stopping means for disconnecting the motor from the power supply and for effecting a disconnect signal at the central ofiice, and means for preventing an opening of the sending contacts and break contacts from interfering with the operation of the disconnect signal, said means including a ground at the subscribers station and an instrumentalityfor connecting the communication line to the ground at the subscribers station during idle periods of the motor.

' WADE B. MARTIN. 

